When an escalator runs, an excessive clearance between the steps and skirt panels at two sides tends to cause foreign matters or fingers and toes of children to be trapped, resulting in damage of the escalator or casualties. In recent years, trapping of fingers, toes or rubber shoes of children in the clearance between the moving steps and skirt panels occurs frequently, which causes personal injuries. When the inspection agency of the quality supervision department carries out supervision and regular inspection on the escalator, the clearance between the steps and skirt panels is also required to be detected, which, according to the requirements of national standard, it should be not more than 4 mm at one side, with the sum of the clearance at both sides being not more than 7 mm.
Currently, however, detection and measurement of the clearance between the steps and skirt panels is generally conducted manually using a filler gauge or a straight steel ruler after the escalator stops at home and abroad since there is no professional detecting instruments and equipment, and there are mainly the following problems: first, there is a difference between the results detected when the steps stop and those when the steps move (due to the shake of the steps when the escalator runs caused by wears of the guide rails and pulleys); second, it is inefficient to perform manual measurement using the steel rule (filler gauge), and thus is difficult to measure all the clearances, so that some hidden dangers may be easily omitted; third, conclusion determinations are easily influenced due to the low resolution of the straight steel ruler and the filler gauge as well as large errors from personnel reading, especially when the data is close to a critical value.